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AoC2023_06.java
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101 lines (85 loc) · 3.26 KB
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import static com.github.pareronia.aoc.itertools.IterTools.zip;
import static java.util.stream.Collectors.joining;
import java.util.Arrays;
import java.util.List;
import java.util.function.Function;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import com.github.pareronia.aoc.solution.Sample;
import com.github.pareronia.aoc.solution.Samples;
import com.github.pareronia.aoc.solution.SolutionBase;
public final class AoC2023_06
extends SolutionBase<List<AoC2023_06.Race>, Long, Long> {
private AoC2023_06(final boolean debug) {
super(debug);
}
public static AoC2023_06 create() {
return new AoC2023_06(false);
}
public static AoC2023_06 createDebug() {
return new AoC2023_06(true);
}
@Override
@SuppressWarnings("unchecked")
protected List<Race> parseInput(final List<String> inputs) {
final List<Long>[] values = IntStream.rangeClosed(0, 1)
.mapToObj(i -> Arrays.stream(inputs.get(i).split(":")[1].split(" "))
.filter(s -> !s.isBlank())
.map(Long::parseLong)
.toList())
.toArray(List[]::new);
return zip(values[0], values[1]).stream()
.map(z -> new Race(z.first(), z.second()))
.toList();
}
@SuppressWarnings("unused")
private long bruteForce(final Race race) {
return LongStream.range(1, race.time())
.filter(t -> t * (race.time() - t) > race.distance())
.count();
}
private long equation(final Race race) {
final double r = Math.sqrt(Math.pow(race.time(), 2) - 4 * race.distance());
final double fx1 = (race.time() - r) / 2d;
final double fx2 = (race.time() + r) / 2d;
final long x1 = fx1 - ((long) fx1) > 0 ? (long) Math.ceil(fx1) : ((long) fx1) + 1;
final long x2 = fx2 - ((long) fx2) > 0 ? (long) Math.floor(fx2) : ((long) fx2) - 1;
return x2 - x1 + 1;
}
private long solve(final List<Race> races) {
return races.stream()
.mapToLong(this::equation)
.reduce((a, b) -> a * b).getAsLong();
}
@Override
public Long solvePart1(final List<Race> races) {
return solve(races);
}
@Override
public Long solvePart2(final List<Race> races) {
final List<Function<Race, Long>> fs
= List.<Function<Race, Long>> of(Race::time, Race::distance);
final long[] a = IntStream.rangeClosed(0, 1)
.mapToLong(i -> Long.parseLong(races.stream()
.map(r -> fs.get(i).apply(r))
.map(String::valueOf)
.collect(joining())))
.toArray();
return solve(List.of(new Race(a[0], a[1])));
}
@Override
@Samples({
@Sample(method = "part1", input = TEST, expected = "288"),
@Sample(method = "part2", input = TEST, expected = "71503"),
})
public void samples() {
}
public static void main(final String[] args) throws Exception {
AoC2023_06.create().run();
}
record Race(long time, long distance) {}
private static final String TEST = """
Time: 7 15 30
Distance: 9 40 200
""";
}